Synthesis of 3,4-Disubstituted 3,4-Dihydro-2-pyrones via 2-(Silyloxy)pyrylium Salts: Regioselective Introduction of Substituents into 2-Pyrones

Article abstract of DOI:10.1021/jo00269a034

Silylation of 4,6-dimethyl- and 6-methyl-2-pyrone with tert-butyldimethylsilyl triflate affords the corresponding 2-(silyloxy)pyrylium triflates 2 quantitatively.Lithium diorganocuprates add regioselectively at position 4 of triflates 2 to give 4-substituted 2-(silyloxy)-4H-pyrans 4.Compounds 4 react with electrophiles at position 3 to give 3-bromo- (8), 3-(silyloxy)- (9), 3-methylene- (15), and 3-(1-hydroxybutyl)-3,4-dihydro-2-pyrones (16).